Since I really can't be bothered reposting all of MIT: Magic Incorporating Technology, you can find the first part
here.
Summary: After the final battle, Harry's magical core was almost exhausted. He decided to leave the magical world behind and instead go to college in America. He chose MIT, where he met a redneck with an affinity for technology. HAsh
Sequel: MIT 02: Apocalypse When?
Summary: After Harry and Ash died taking out Azazel, things gradually went back to normal for the Winchesters. Now, eighteen months later, they've been approached by the angel Castiel with a task: Get Harry back from Death's domain so that he can fulfil his task as vessel to an angel. Getting Harry back is only part of the battle though - Harry won't come back without Ash, and he's bound to be upset about the whole vessel thing. But if it'll stop an apocalypse… he's still not happy. The angel wanting to possess him is going to have to do some pretty drastic negotiating.
Pairings: Harry/Ash (obviously), Ron/Hermione, some one-sided Sam/Hermione. Perhaps others as the story progresses.
Chapter One: That Could Be Inconvenient Chapter Two: Well That Went Well Chapter Three: You Lost One? Chapter Four: Is Every Male in America Gay?